In a technology region where an image is formed according to an electrographic method, an electrostatic charge image developing toner has been fixed on a recording medium such as paper through heating and pressurization using a fixing roller. To achieve energy saving upon fixation and apparatus downsizing, there have been demands for an electrostatic charge image developing toner that can be fixed at lower temperature and that has excellent low-temperature fixability. In the electrostatic charge image developing toner with the excellent low-temperature fixability, a binder resin with a low softening point (Tm) and a low glass transition point (Tg) and a releasing agent with a low softening point have been used. Thus, in a situation in which the electrostatic charge image developing toner is stored under high temperature, there arises a problem that toner particles included in the electrostatic charge image developing toner are likely to aggregate. Then a charge amount of the aggregating toner is more likely to decrease than that of a non-aggregating toner, and thus the aggregating toner is unnecessarily likely to be developed. This may consequently cause an image default.
The electrostatic charge image developing toner includes a plurality of toner particles. Each of the toner particles is typically obtained through a blending process of blending components such as a releasing agent, a colorant, a charge control agent, and a magnetic powder with a binder resin, a kneading process, a pulverization process, and a classifying process.
A method has been suggested for manufacturing an electrostatic charge image developing toner and including a process of aggregating particles obtained by polymerizing monomers containing a binder resin and a process of forming a shell layer on surfaces of the aggregated particles (for example, Patent Literature 1).